Relay apparatus



Aug. 12, 1941. w. D. COCKRELL 2,252,457

RELAY APPARATUS Filed July 13, 1940 Inventor": William DCockreH, b JV X9His ttorney Patented Aug. 12, 1941 UNITED STATES PATENT OFFICE RELAYAPPARATUS New York Application July 13, 1940, Serial No. 345,425

3 Ciaims.

My invention relates to relay apparatus and particularly to relayapparatus of the type employing electron discharge amplifying means.Such apparatus often is employed to control an electro-magnetic relay ofsome common, inexpensive form. It sometimes happens that where theapparatus is required to respond to impulses of very short duration thetime constant of the electromagnetic relay employed is too great toenable the relay to respond to the impulses. If the impulses are not tooshort, a special form of high speed relay may be successfully used;however, the additional cost of such a relay is an importantconsideration in many cases and there is a limit to the shortness of theimpulses to which even such relays will respond.

It is the object of my invention to provide improved relay apparatusfrom which one may operate an ordinary inexpensive form ofelectromagnetic relay or other responsive device which apparatus willcause the operation of the relay in response to impulses, no matter howshort, received by the apparatus. In accord ance with my invention, Ihave devised a form of relay apparatus having improved means for solengthening each received impulse that an ordinary, inexpensive relay orresponsive device can be successfully used therewith.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing and its scope will bepointed out in the appended claims.

In the single figure of the drawing which is a circuit diagram of oneembodiment of my invention, the transformer I whose primary may beenergized from a 115 volt 60 cycle lighting circuit is shown feedingthrough the rectifiers 2 a Well known form of two stage direct currentamplifier circuit having the positive side 3, the negative side 4 andthe neutral or ground side 5. The electron discharge amplifier 1 has itsanode connected through the resistor 8 with the positive side 3 and itscathode connected through the resistor 9 with the ground lead 5. Avoltage divider comprising the two resistors l and the potentiometer llconnects between 3 and 4, the adjustable arm l2 of the potentiometerbeing connected with the ground side 5. A negative bias is supplied tothe control grid I3 of the amplifier 1 from the lower or negative end ofthe potentiometer through the resistor '14. In the form of my inventionwhich I have chosen to illustrate, the impulse to be amplified isobtained from the photo-electric device l5 connected between the side 3and the grid l3. As so arranged, as long as the photoelectric device isilluminated the negative bias is opposed and the amplifier 1 passescurrent.

The electron discharge amplifier [1 has its anode connected with theside 3 through the Winding of the electromagnetic relay [8, which may beof inexpensive construction and not particularly fast in operation. Thecathode of this amplifier connects with the cathode of the amplifier l,the two amplifiers thereby having the common cathode resistor 9 wherebyI am able to obtain quicker closing and opening of the relay. I am ableto operate the two amplifiers in cascade with the two cathodes at thesame potential in as much as I use a voltage divider comprising theresistors l9 and 20 between the anode of l and the side 4 to whichdivider the control grid of IT connects through the resistor 2|.

The screen grid 23 of the amplifier ll connects with the side 3 throughthe resistor 24 which may have a resistance of 5000 ohms. Connectedbetween the screen grid 23 and the ground side 5 is the capacitor 25,which may have a capacitance of 0.25 mid, and the resistor element 26,which may have a resistance of 0.5 meg., of the potentiometer 21. Theadjustable arm 28 of the potentiometer connects with the suppressor grid29 of the amplifier 1. Thus it will be seen that I have provided a feedback circuit from the screen grid of the second amplifier to thesuppressor grid of the first amplifier.

The operation of the apparatus illustrated briefly is as follows: Whenthe photo-electric device is illuminated the amplifier l carries currentbut the amplifier I! does not, at least does not carry sufficientcurrent to operate the relay I8. Should a sudden reduction occur in theillumination lasting for only a short interval, shorter even than thatnormally required for the operation of the relay [8, the amplifier 'l byhaving its impedance increased ceases to conduct and the amplifier I! byhaving its impedance decreased by reason of its coupling therewithaccordingly is made to conduct. This lowered impedance of I! results inan increase in the current passing to the screen grid 23 thereof throughthe resistor 24 and because of the potential drop through that resistora reduced voltage is applied to the capacitor 25. The freed negativecharge on that plate of the capacitor which connects with the suppressorgrid 29 swings that grid sufiiciently negative to produce a highimpedance condition in the amplifier 'l regardless of the control gridl3 which now has lost control. This condition of high impedance of 'Iand accordingly low impedance of 11 continues until the former highercharge on the capacitor has had time to reduce by discharging throughthe potentiometer 26 and amplifier H to the new lower value. The lengthof this time may be very materially longer than the length of theimpulse of reduced light and is suificient to permit the operation ofthe relay 18. When the charge on the capacitor in reducing finallyreaches a fixed or nearly fixed value the suppressor grid 29 returnssubstantially to cathode voltage whereupon the grid l3 regains controlrestoring the amplifier to its original low impedance or conductingcondition. Amplifier ll consequently is returned to its original highimpedance condition and the relay I8 is deenergized.

It will thus be seen that an extremely short impulse applied to thecontrol grid of the first amplifier produced, for example by acorrespondingly short interruption or decrease in light afiecting thephoto-electric device by cumulative action causes a current impulse tobe supplied to the relatively slow load device of ample length to insurethe proper operation thereof. An advantage of using the voltage obtainedfrom the screen grid rather than from the anode of the second amplifierfor efiecting the change in capacitor charge is that its load is pureresistance whereas the anode load is'largely inductive and as such ismore influenced by ripples in the rectified direct current supply, etc.By varying the position of the potentiometer arm 28 I may vary thelength of the output impulse of amplifier ll made in response to a givenshort input impulse to amplifier '1.

While I have shown and described the photo electric device as connectedin a manner to operate the relay (8 in response to a brief lightdecrease it will be obvious to one skilled in the art that it may berearranged if so desired to operate the relay in response to a brieflight increase instead.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Relay apparatus comprising a first electron discharge amplifierhaving a control grid and a suppressor grid, a second electron dischargeamplifier connected in cascade with said first amplifier and having ascreen grid, a resistance supply connection to said screen grid, a loaddevice in the output circuit of said second amplifier, means by which animpulse may be applied to the control grid of said first amplifier of alength shorter than that required for the actuation of said load device,a resistance connection between the suppressor grid and the cathode ofsaid first amplifier and a capacitor connection between said suppressorgrid and said screen grid.

2. Relay apparatus comprising a first electron discharge amplifierhaving a control grid and a suppressor grid, a second electron dischargeamplifier connected in cascade with said first amplifier and having ascreen grid, a resistor in the supply connection to said screen grid, aload device in the output circuit of said second amplifier, means bywhich an impulse may be applied to the control grid of said firstamplifier of a length shorter than that required for the actuation ofsaid load device, variable resistance means between the suppressor gridand the cathode of said first amplifier and a capacitor connectedbetween said suppressor grid and said screen grid.

3. Relay apparatus comprising a first electron discharge amplifierhaving a control grid and a suppressor grid, a second electron dischargeamplifier having its control grid connected with the output circuit ofsaid first amplifier and having a screen grid, a resistor in the supplyconnection of said screen grid, an electro-magnetic load device in theoutput circuit of said second amplifier, a photo-electric device forapplying an impulse of short duration to the control grid of said firstamplifier, a potentiometer having its arm connected with the suppressorgrid of said first amplifier and one end connected with the cathodethereof and a capacitor connected between the other end of saidpotentiometer and the screen grid of the second amplifier.

W'ILLIAM D. COCKRELL.

